No Man's Sky/Wanted levels

A wanted level is how high a threat the sentinels think you are. It starts at zero, where they won't attack you, except on extreme sentinel planets, but it will be set to one by doing certain things:

Attacking a sentinel
Letting a sentinel scan you on an extreme sentinel planet
Continuing to mine resources while a sentinel is watching you
Attacking resource pods or reinforced doors in supply depots and secure facilities
Destroying a freighter cargo pod
Destroying any non-pirate starship
Attacking the space station (won't use the same wave system as mentioned below)
Get caught with smuggled contraband during an inventory scan, and refusing to give them up

It will be set to three by collecting a gravitino ball (unless you farmed it yourself).

Attacking the space station, by accident or on purpose, will summon sentinels from the station, and they don't stop. This is a good way to farm their drops, as you can board the space station to escape them.

As your wanted level sets to one, nearby sentinels will immediately become hostile. Destroying all of them will bring reinforcements. Either run, or hide, if you want to escape.

Wave types

What type of waves you get depend on whether you are in your starship or not. Some actions can only be triggered in a starship, most only on ground, some in both.

You can stop sentinels attacking you in space by entering the space anomaly, your freighter, or the space station. However, your freighter and the anomaly cannot be summoned (or dismissed) during combat.

Waves - on the ground

First you need to destroy all nearby sentinels, then reinforcements will appear. If you are scanned an an extreme sentinel planet, or there are no nearby sentinels when you angered them, wave one begins immediately. Otherwise, wave one begins after a 10 second countdown, saying "reinforcements arriving" (once all nearby hostile sentinels are killed). Running will cause them to lose you, and they will search for you. If you can stay hidden for a certain amount of time (which depends on the wave, being 13 seconds at wave one, and up to sixty on wave five), your wanted level resets to 0, and any sentinels that were chasing you will turn peaceful again.

The first wave is quite simple: a few healing sentinels and combat sentinels. Take the healers out first. They are the small black ones. Take out the combat ones (they are larger and orange) afterwards.

Killing all the wave one sentinels will increase your wanted level, and give you up to 10 seconds to escape or prepare. This next one is a lot like wave one, but with more sentinels. Sentinel summoners (black triangular ones) will occasionally summon two more combat sentinels, so they should be taken out first.

Wave three is tougher, with 10 seconds to escape or prepare. It is like wave 2, but you also need to deal with a dog-like sentinel. Try to get high ground, maybe on a building, and shoot down the flying ones first. Then take out the dog-sentinel.

Wave four is really tough, with 6 seconds to escape or prepare, and having loads of flying sentinels and a large mech. Take out the flying ones first, especially the healers and summoners. The mech shoots lasers at you, and even has a flame thrower at half health. Aim for the black spots, since they are weak points.

Wave five is the hardest wave, with only 3 seconds to prepare. You are unlikely to be able to escape in that time. A dog, a mech, and maybe 15 flying sentinels are fighting you. If you thought that was hard, wait until you see what else you've got to face: a massive, fifty-foot armoured walker. After taking out some of the smaller targets (mainly the healers, summoners, the dogs, and the mech), aim for the back or top of the head of the walker. Anywhere else is impervious to attack.

Completing wave 5 will temporarily disable sentinels on the planet, set you wanted level back to 0, and show you were the sentinel nest, now unguarded, is. But before you rush off, consider collecting your rewards first. Combat sentinels, dog sentinels, and sentinel meches all drop a round pod of valuable resources. Nanites, ammo, salvaged glass, and more, can be found. Walkers also drop their pieces, and the large piece (their body) can be destroyed for more loot.

Consider also going to the marked sentinel pillar, since they have resource pods of rare sentinel drops, and a terminal can be interacted with to collect information about the history of the sentinels, from their point of view. You can also use the pillar to extract a new multitool as well.

Waves - in space

It is less easy to fight sentinels in space, and the recovered loot is limited, but at least you need to face less of them.

Wave one: you need to destroy one single sentinel interceptor.

Wave two: you need to fight two sentinel interceptors.

Wave three: you need to destroy three stronger sentinel interceptors.

Wave four: you need to destroy a larger amount of sentinel interceptors.

Wave five: you fight maybe 10 sentinel interceptors, not all at once, and a freighter with loads of turrets on it. Take out the turrets and a few interceptors. Attacking the freighter damages it, and if you deal enough damage, it will explode, causing all sentinel interceptors to flee.

In between each wave, you have a short time where you can pulse jump away, or better (sentinels can still drag you out of a pulse jump when more arrive): enter a space station/freighter/the anomaly. If that cannot be done, your only hope it to fight, or activate an emergency warp. After activating the emergency warp, remember to repair the emergency warp drive starship upgrade.

Salvaged glass

This item acts a bit like geodes. When broken in your inventory, they can drop powerful upgrades, sentinel pillar planetary charts, pungeum and other sentinel drops.

Sentinel upgrades are very powerful. They target up to four stats, mostly combat related, and the maximum increase is quite high. They come in multitool upgrades and exosuit upgrades. Despite what the word "forbidden" on the tooltip may suggest, having or equipping one will not anger sentinels.